1. Field of the Invention
The present invention relates to an apparatus and method for detecting non-recording regions of an optical recording medium, and more particularly, to an apparatus and method for detecting non-recording regions of an optical recording medium for recording data or reproducing the recorded data by detecting header regions of the optical recording medium.
2. Description of the Background Art
Generally, an optical recording/reproducing apparatus records or reproduces data on an optical recording medium such as a CD (Compact Disc), DVD-RAM (Digital Versatile Disc-Random Access Memory), etc. The above-mentioned optical recording medium has a track structure consisting of a land and groove. Particularly, a rewritable optical recording medium such as the DVD-RAM records data signals on the land and groove, respectively, in order to increase data recording density. To record data on the land and groove, the optical recording/reproducing apparatus must reduce the size of a laser beam spot for recording and reproducing data by decreasing the wavelength of a laser light outputted from an optical pickup and increasing the numerical aperture of an objective lens of the optical pickup.
FIG. 1 is a block diagram of a general optical recording/reproducing apparatus, wherein an optical recording medium for recording data on a land and groove is mounted on a drive of the above optical recording/reproducing apparatus.
To record or reproduce data on the optical recording medium, optical pickup 102 is operated by control of servo control unit 106 through focus servo driving unit 107 and tracking servo driving unit 108, and accordingly outputs laser beams onto a signal recording surface of the optical recording medium 101 on which data is recorded. When the light reflected from the signal recording surface of the optical recording medium is incident on the optical pickup again, the optical detector installed in the optical pickup outputs electric signals to the RF and servo error generating unit 104.
RF and servo error generating unit 104 outputs focus error signals, tracking error signals, and RF signals (lead channel 1 signals) upon receipt of the electrical signals. Herein, the focus error signals (FE) and the tracking error signals (TF) (lead channel 2 signal) are generated from the electric signals outputted from the optical detector comprised of a plurality of optical detection devices.
The lead channel signals 1 outputted from RF and servo error generating unit 104 are outputted to decoder 105, and the FE signals and TE signals are outputted to servo control unit 106. Namely, decoder 105 restores the RF signals to the original data when it reproduces the data recorded on the optical recording medium.
Encoder 103 receives data to be recorded on the optical recording medium. That is, encoder 103 encodes the data to be recorded using recording pulses appropriate to the type of optical recording medium 101, and thereafter records the encoded data on optical recording medium 101 through optical pickup 102.
Meanwhile, the above-described optical recording/reproducing apparatus can be connected to a host such as a PC. In the optical recording/reproducing apparatus connected to the host, when a recording/reproducing command transmitted from the host through interface 110 is inputted to microcomputer 111, the data to be recorded on optical recording medium 101 is transmitted to encoder 103 to thus be recorded on optical recording medium 101 by control of microcomputer 111, and the data outputted from optical recording medium 101 is transmitted from decoder 105, for thereby reproducing the data recorded on optical recording medium 101.
Servo control unit 106 outputs control signals to focus servo driving unit 107 and tracking servo driving unit 108, respectively, upon receipt of the focus error signals (FE) and tracking error signals (TE). Focus servo driving unit 107 drives a focus actuator in optical pickup 102 to move optical pickup 102 upwardly and downwardly, and makes beams outputted from optical pickup 102 to follow tracks of optical recording medium 101 as optical recording medium 101 is rotated and at the same time moved upwardly and downwardly, being focused on the track of optical recording medium 101. In addition, tracking servo driving unit 108 drives a tracking actuator in optical pickup 102 to move the objective lens of optical pickup 102 in the radial direction, thereby correcting the position of the beams and following the tracks.
Meanwhile, in the case of optical recording medium 101 such as DVD-RAM which is directly delivered from its manufacturer and has no information recorded, the optical recording/reproducing apparatus cannot record any data on optical recording medium 101 because optical pickup 102 cannot access optical recording medium 101. Therefore, in order to record data on optical recording medium 101, optical recording medium 101 must have land and groove tracks. On optical recording medium 101 having the above tracks, control information for sector addressing, random access, and rotation control is recorded along with the tracks on which data is recorded, being separated from the above-mentioned data to be recorded, thus making it possible to control the tracking of optical recording medium 101 having no recorded data thereon. Namely, the above-mentioned control information can be recorded by pre-formatting header regions on the starting position of each sector or by forming wobble along with the tracks.
Here, the above-mentioned wobble is information recorded on the optical recording medium by modulating certain clocks, including the information on the corresponding position and rotational speed of the optical recording medium, which is analyzed by optical power detected by a laser diode of the optical pickup.
FIG. 2(a) is a view illustrating a header region pre-formatted on the starting position of each sector of the optical recording medium, said header region having four header fields (header 1 fieldxcx9cheader 4 field).
The header 1 and 2 fields and the header 3 and 4 fields are arranged in a staggered fashion with each other from the center of the tracks. The phase of the header 1 and 2 fields is opposite to that of the header 3 and 4 fields, and also the phase of tracking error signals detected from the header 1 and 2 fields is opposite to that of tracking error signals detected from the header 3 and 4 fields. The track interface of regions whose data is recorded on the optical recording medium is, as illustrated in FIG. 2(a), formed in a wobble shape.
In the structure of the header region of the optical recording medium described above, servo error signals such as tracking error signals and focus error signals are generated. That is, the servo error signals read out from the header regions are distorted according to the structure of the header regions, and it is difficult to control the distorted servo error signals.
Therefore, in the case of optical recording medium such as DVD-RAM, the servo of the optical recording/reproducing apparatus is performed so that the servo error signal is held in the header regions, in order to reduce the influence on the servo error signals according to the header structure. That is, in the header region section, the beams outputted from the optical pickup are made not to deviate from the center of the tracks of the optical recording medium by covering the header regions with header masks and holding the tracking error signals
For this purpose, it must be firstly judged that the information reproduced by the optical recording apparatus belongs to the header regions of the optical recording medium. The header regions are judged by using wobble signals detected from lead channel 2 signals and IP1 or IP2 signals. Herein, since the number of wobble signals existing on each sector is always constant, header mask signals are generated by counting the number of the wobble signals. At this time, the wobble signals may not be detected well because of defects of the optical recording medium. Thus, as illustrated in FIG. 2(e), header mask signals are generated by counting the number of clocks that are phase-locked on the wobble signals actually recorded on the optical recording medium, that is, the number of PLL-wobble signals.
As illustrated in FIG. 2(d), the rising timing of the header mask signal is determined by counting the number of PLL-wobble signals as illustrated in FIG. 2(e) from the falling timing of the previous header mask signal, and, as illustrated in FIGS. 2(b) and 2(c), the falling timing of the header mask signal is determined by using IP1 or IP2 signals.
At this time, since the header 1 and 2 fields and the header 3 and 4 fields are arranged in a staggered fashion with each other from the center of the tracks of the optical recording medium, the phase (slope) of lead channel 2 signals detected from the header 1 and 2 fields is opposite to that of lead channel 2 signals detected from the header 3 and 4 fields. If the lead channel 2 signal of the header region is above the center of the track, it is outputted to a IP1 signal waveform as illustrated in FIG. 2(b) and, if it is below the center of the track, it is outputted to a IP2 signal waveform as illustrated in FIG. 2(c).
When data is recorded/reproduced on the optical recording medium, the phase is changed to the above IP1 signal or IP2 signal according to whether the currently followed track is a land or a groove. That is, either IP1 signal or IP2 signal is firstly outputted according to whether the track is a land or a groove. At this time, the falling timing of the header mask signal can be determined by ORing the above IP1 signal and IP2 signal. The lead channel 2 signal is detected when both tracking servo and focus servo are ON because the servo of the optical recording/reproducing apparatus is stably performed.
If the tracking servo is in the traverse state or free-running state, the servo of the optical recording/reproducing apparatus is unstable. Thus, the lead channel 2 signal is not detected, and accordingly the IP1 or IP2 signal is also not detected. Subsequently, if there are no IP1 and IP2 signals which are used as reference signals, the header regions are not properly detected and accordingly the servo error signals cannot be held in the header region, whereby the servo error signals are more influenced by the header regions.
In this way, when the IP1 or IP2 signal is used for measuring the traverse or eccentric amount for seeking by holding the header regions, the servo error signals are distorted because free running occurred due to the header regions.
If the tracking error signals cannot be held in the header regions, the tracking error signals become larger and the actuator follows the header regions. If the actuator follows the header regions, track slippage occurs thereby making the track servo unstable due to discrete track error variation and degrading the characteristics of recording/reproducing data on the optical recording medium.
Accordingly, it is an object of the present invention to provide an apparatus and method for detecting non-recording regions of an optical recording medium for recording or reproducing data by precisely detecting header regions of the optical recording medium even in the case that a servo is unstable.
For this purpose, in the apparatus for detecting non-recording regions of the optical recording medium having a plurality of header regions of different phases arranged between writable data regions in which the information capable of recognizing a reference frequency is wobbled on tracks, in order to distinguish the data regions by their shapes, the apparatus for detecting non-recording regions of the optical recording medium in accordance with the present invention includes a header region detection unit for detecting the plurality of header regions, a header region verification unit for verifying the detected header regions and outputting verified signals, a wobble-PLL unit for outputting PLL-wobble signals by phase locking upon receipt of wobble signals recorded on the tracks of the optical recording medium, and a counter for outputting header mask signals by counting the number of output pulses of the wobble-PLL unit upon receipt of the PLL-wobble signals on the basis of the verified signals.
In the method for detecting non-recording regions of the optical recording/reproducing apparatus having a plurality of header regions of different phases arranged between writable data regions in which the information capable of recognizing a reference frequency is wobbled on tracks, in order to distinguish the data regions by their shapes, the method for detecting non-recording regions of the optical recording medium in accordance with the present invention includes a step of generating first header detection signals and second header detection signals by generating control signals by using optical reflection signals from the optical recording medium and slicing the control signals to a set slice level, a step of generating a verification signal for determining header mask regions by using the first and second header detection signals, and a step of determining the xe2x80x9conxe2x80x9d time point of the header mask signal representing a header region by counting the number of PLL-wobble signal generated by locking a phase lock loop (PLL) on the wobbling signals and determining the xe2x80x9coffxe2x80x9d time point of the header mask signal by using the verification signal as the reference signal.